This invention relates to improvements in one-piece metal door frames of the type having a pair of opposed jambs and a connecting header, which frames incorporate a central soffit, a pair of flanking stops, rabbets flanking said stops, and trim faces flanking said rabbets, and improvements in methods of assembling same.
As is known to the trade, the major components of such frames, which are jambs and headers, are customarily shipped to an assembly plant (near the site of proposed use in construction) to be assembled and further transported to the job site. Also, as known to the trade, cooperating metal tabs and slots are provided in the appropriate ends of the jambs and header to facilitate forming the frame corners which are then welded to make the junction stronger. In the prior art method the corners are squared by measurement, a weld is made on the joint, the jambs might or might not be braced, and a load of frames is trucked to the construction job site.
The resulting frame assembly is often out of square when it leaves the assembly plant or becomes so after handling en route to or at the job site.
The problem of dealing with imperfectly aligned frames has been customarily dealt with on the job site as a building construction problem, and the usual strategems and devices used at the job site are directed primarily at preventing further deformation of the frame after it is positioned in a doorway; e.g., from grout, twisted studs and shifting of doorway wall opening elements.
Accordingly, various devices for use at the job site have been made to correct defects, and to prevent further deviation caused by on-site stresses such as pressure from poured concrete, and to compensate for out of square door openings.
Some success at squaring the frame and keeping the frame members in the same plane after installation has been achieved at the job site, but truing of the frame after the frame leaves the assembly plant is difficult and of limited success.
Also, factory jambs ordinarily have a camber (the curve that a long section of formed thin steel assumes when responding to the stresses created by forming with a press break o by roll forming) as a result of the break form or roll form step at the factory, the latter condition either not being known or not understood or treated properly at the local assembly plant.